CN1643585A - Inclination detector, optical head, optical information processor, computer, video recorder, video reproducer, and car navigation system - Google Patents

Abstract

The light emitted by the light source (1) is separated into a main light beam and at least two secondary light beams by an optical separation device (2). The converging optical system (6) converges the main beam and the sub-beam near the optical disc (7), while making their focus positions different from each other in the direction of the optical axis of the converging optical system (6) and the direction orthogonal thereto. The detecting device (9) detects the relative inclination angle of the optical axis of the optical disc (7) and the converging optical system (6) by detecting the size of the light spot of the sub-beam reflected by the optical disc (7) on the detecting device (9). In this way, the relative inclination of the optical axis of the optical disc (7) and the optical head can be detected with high precision without increasing the size and cost of the optical head.

Description

Inclination detection devices, optical heads, optical information processing devices, computers, video recording devices, video reproducing devices, and car navigation systems

technical field

The invention relates to an inclination detection device for detecting the relative inclination between an optical information recording medium such as an optical disc or an optical card and an optical pick-up. Furthermore, the present invention also relates to an optical head and an optical information processing device having the inclination detection device, recording, reproducing or erasing information on an optical information recording medium.

In addition, the present invention also relates to a computer, a video recording device, a video playback device, and a car navigation system, which include the optical information processing device as a storage device.

Background technique

In recent years, with the development of optical disc technology, various optical discs such as re-recordable optical discs and read only (ROM) optical discs have been put into use. Under such circumstances, various schemes have been proposed for detecting the relative inclination between the optical head and the optical disc as a result of disc warping, which is one cause of deterioration of the quality of the light spot on the optical disc.

Fig. 6 shows the structure of the optical head loaded with the device for detecting the relative inclination between the optical head and the optical disc. In FIG. 6 , laser light emitted from a semiconductor laser 101 is reflected by a prism 103 , becomes parallel light through a collimator lens 104 , and is converged by an objective lens 105 to form a light spot on the information recording surface of an optical disc 106 . Then, the light reflected by the optical disk 106 passes through the objective lens 105 again and passes through the collimator lens 104 , the prism 103 , and the cylindrical lens 108 , and then enters the photodetector 109 . In the prior art, a tilt sensor 110 for detecting a relative inclination between the optical head and the optical disc 106 caused by bending of the optical disc 106 or the like is provided on the head base 111 . The tilt sensor 110 includes a light-emitting diode 112 and light-receiving devices 113 and 114 arranged to sandwich the component. The light emitted by the light emitting diode 112 is reflected by the optical disk 106 and then received by the light receiving devices 113 and 114 . The relative inclination angle is detected from the output difference of the photodetectors 113 and 114 .

As mentioned above, in order to detect the relative inclination angle of optical disc and optical pick-up, existing optical pick-up is provided with inclination sensor 110 for tilt angle detection on the head base 111 of optical pick-up, has just caused like this optical pick-up Large size and high cost.

In order to solve the above-mentioned problems, in Japanese Patent No. 2827186 (Title of the Invention: Optical Disc Curvature Detection Method and Optical Pickup), the relative inclination of the optical disc and the optical pickup is detected as follows. That is, the light emitted from the semiconductor laser is separated into three beams of the main beam and its left and right sub-beams, and the three beams are irradiated on the signal surface of the optical disc so that their respective light spots extend from the center of the optical disc. Arranged on the radius line. Each return light reflected from the disc is guided to an optical component that produces astigmatism, and the left and right sub-beams among the three beams transmitted through the optical component are received by two 4-splitting sensors for tilt angle detection. Utilizing the output of the above-mentioned 2 inclination detection 4-splitting sensors, the positive or negative defocus of the two sub-beams on the signal surface of the optical disc generated by the relative inclination of the optical disc and the optical pickup is detected by the astigmatism method, so that it can be detected The relative inclination of the optical disc and photodetector. In the above configuration, it is necessary to guide the return light from the optical disk of the two sub-beams for inclination detection to the centers of the two four-splitting sensors. However, when the wavelength of the semiconductor laser changes due to temperature changes, the optical axis of the sub-beam changes, and the return light is incident on a position deviated from the center of the 4-splitting sensor. As a result, an error occurs in the signal for inclination detection.

Contents of the invention

In order to solve the above problems, the object of the invention of the present application is to provide a tilt detection device, which can detect the optical axis between the optical information recording medium and the optical head without enlarging the size of the optical head and increasing the cost. The relative inclination angle of the optical information recording medium and the optical head can be stably detected without being affected by the change of the laser wavelength caused by the temperature change. In addition, the object of the present invention is also to provide an optical head and an optical information processing device using the tilt angle detection device, and a computer, a video recording device, a video reproducing device, and an automobile equipped with the optical information processing device as a storage device. Navigation System.

The inclination detection device of the present invention comprises: a light source; a converging optical system for converging light beams from the light source on an optical information recording medium; an optical separation device for separating the light beams from the light source into a main beam and at least two sub-beams and detecting means for detecting reflected light from the optical information recording medium, the focus position of the first converging light of the main beam towards the optical information recording medium, and the sub beam towards the optical information recording medium The focus positions of the second converged light are different from each other in the direction of the optical axis of the convergent optical system and in the direction perpendicular to the direction of the optical axis. By using the detection device, the The reflected light reflected on the optical information recording medium is detected by the size of the light spot formed on the detecting device, so as to detect the relative inclination between the optical information recording medium and the optical axis of the converging optical system.

An optical head of the present invention includes the above-mentioned inclination detection device of the present invention.

The optical information processing device of the present invention includes: the above-mentioned optical head of the present invention; a drive mechanism for moving the optical information recording medium relative to the optical head; and a control circuit for controlling The optical head and the driving mechanism.

A computer of the present invention includes the optical information processing device of the present invention described above.

A video recording device of the present invention includes the above-mentioned optical information processing device of the present invention.

A video playback device of the present invention includes the optical information processing device of the present invention described above.

A car navigation system of the present invention includes the optical information processing device of the present invention described above.

Description of drawings

FIG. 1 is an example of the structure of an optical head according to Embodiment 1 of the present invention.

FIG. 2 shows an example of the arrangement of a photodetector light-receiving unit of the optical head according to Embodiment 1 of the present invention.

3A and FIG. 3B are explanatory diagrams of the relative inclination detection method between the optical disc and the optical head optical axis of the present invention. FIG. 3B is a plan view of the light spot on the light receiving part of the photodetector in a state where the optical axis of the optical head is not perpendicular to the optical disc surface (a state of relative inclination).

4A～4C show the structural example of the plate optical element (hologram) that produces the main beam and the sub-beam on the optical head of Embodiment 1 of the present invention, FIG. 4A is its top view, and FIG. 4B is along the line 4B- A cross-sectional view of line 4B, and Fig. 4B is a bottom view thereof.

FIG. 5 is a schematic configuration diagram of an optical disc drive according to Embodiment 2 of the present invention.

Fig. 6 is a structural diagram of an example of a conventional optical head.

Detailed ways

According to the inclination detection device of the present invention, the relative inclination of the optical axis of the optical information recording medium and the optical head can be detected without enlarging the optical head or increasing the cost, and it is not affected by the laser wavelength caused by temperature changes. The relative inclination angle between the optical information recording medium and the optical head can be detected stably without the influence of fluctuations.

In the inclination detection device of the present invention described above, the distance between the focus position of the first converged light and the focus position of the second converged light in the direction of the optical axis of the converging optical system is Z When the distance in the direction perpendicular to the optical axis of the converging optical system is X, the X and the Z preferably satisfy 0.08>Z/X>0.008. In this way, the relative inclination angle between the optical information recording medium and the optical head and the optical axis can be detected within the range of 0.5° to 5°.

In addition, in the inclination detection device of the present invention described above, it is preferable that the light receiving unit of the detection device which receives the reflected light reflected by the sub-beam on the optical information recording medium is divided into three parts by a dividing line. In an area, the dividing line is substantially parallel to a plane including the focus positions of the reflected lights reflected by the main beam and the sub-beam on the optical information recording medium. In this way, even if the focal lengths of ±1st order light and 0th order light change due to temperature changes, the inclination detection signal is not affected.

In addition, in the above-mentioned inclination detection device of the present invention, the optical separation device is a simple diffraction grating. In this way, ±1st-order light (sub-beams) for inclination detection can be obtained.

Alternatively, in the above-mentioned inclination detection device of the present invention, the optical separation device may also be a plate-shaped optical element, and the plate-shaped optical element is provided with a first comprehensive diffraction pattern with curvature on the first surface; A second comprehensive diffraction pattern is provided on the second surface opposite to the first surface, and the second comprehensive diffraction pattern is symmetrical to the first comprehensive diffraction pattern relative to the axis parallel to the first surface; And the cross-sectional shape of the second comprehensive diffraction pattern is saw-toothed or stepped. In this way, by changing the pitch and radius of curvature of the integrated diffraction pattern, the distance between the focus position of the 0-order light (main beam) for reproduction signal detection and the focus position of ±1-order light (sub-beam) for tilt angle detection can be changed. (the above distance X and distance Z), and thus the range of detectable inclination angles can be freely designed.

An optical head of the present invention includes the above-mentioned inclination detection device of the present invention. In this way, when the relative inclination occurs between the optical axis of the optical information recording medium and the optical head due to the curvature of the optical information recording medium, etc., it is also possible to correct the coma aberration according to the inclination detection signal, thereby performing a good recording or reproducing operation. .

The optical information processing device of the present invention includes: the above-mentioned optical head of the present invention; a drive mechanism for moving the optical information recording medium relative to the optical head; and a control circuit for controlling the optical head and the drive mechanism. In this way, when the relative inclination occurs between the optical axis of the optical information recording medium and the optical head due to the curvature of the optical information recording medium, etc., it is also possible to correct the coma aberration according to the inclination detection signal, thereby performing a good recording or reproducing operation. .

Any one of the computer, video recording device, video reproducing device and car navigation system of the present invention has the optical information processing device of the present invention described above. In this way, when the relative inclination occurs between the optical axis of the optical information recording medium and the optical head due to the curvature of the optical information recording medium, etc., it is also possible to correct the coma aberration according to the inclination detection signal, thereby performing a good recording or reproducing operation. .

The present invention will be described in detail below through specific examples.

(Embodiment 1)

An optical head according to Embodiment 1 of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of an optical head according to Embodiment 1 of the present invention. 1 is a semiconductor laser as a light source, 2 is a diffraction grating (or also called a simple diffraction grating) as an optical separation device, 3 is a polarizing beam splitter, 4 is a collimating lens, 5 is a λ/4 plate, and 6 is an objective lens , 7 is an optical disc, 8 is a half mirror, 9 and 11 are photodetectors as detection devices, and 10 is a cylindrical lens.

Hereinafter, the operation of the optical head of the first embodiment will be described with reference to FIG. 1 . The linearly polarized light beam emitted from the semiconductor laser 1 is separated by the diffraction grating 2 into transmitted 0-order light and diffracted ±1-order light. After the 0-order light and ±1-order light are reflected by the polarizing beam splitter 3, they pass through the collimator lens 4 and become substantially parallel light, and then pass through the λ/4 plate 5 to become circularly polarized light and then enter the objective lens 6, and are transmitted to the optical disc. Convergence on 7. At this time, as shown in the figure, the 0th-order light as the main beam is focused on the information recording surface of the optical disc 7, and the ±1st-order light as the sub-beams is focused at a position deviated from the information recording surface of the optical disc 7 toward the objective lens 6 side. When the distance in the direction of the optical axis of the objective lens 6 between the focus position of the zero-order light and the focus position of ±first-order light is Z, and the distance in the direction perpendicular to the optical axis is X, set It is defined as satisfying the condition of 0.08>X/Z>0.008 (forward journey).

The 0-order light and ±1-order light reflected by the optical disc 7 return to the original optical path, pass through the λ/4 plate 5 and become linearly polarized light perpendicular to the polarization direction of the light beam emitted from the semiconductor laser 1, and then pass through the polarized light beam The splitter 3 is separated into transmitted light and reflected light by a half mirror 8. The transmitted light is incident on the photodetector 9 . The reflected light is incident on the photodetector 11 after passing through the cylindrical lens 10 . The photodetector 9 detects the relative inclination of the optical axis of the optical disc 7 and the optical head (that is, the optical axis of the objective lens 6 ), and the photodetector 11 detects a servo signal (return) such as a focus error signal.

The shape of the photodetector 9 will be described below with reference to FIG. 2 . The light-receiving part A of the photodetector 9 receives 0-order light, and the light-receiving part B and the light-receiving part C receive +1-order light and −1-order light, respectively. As shown in the figure, the light receiving part B and the light receiving part C are respectively divided into three parts by the dividing lines 9b and 9c substantially parallel to the plane containing the focal positions of the 0-order light and the ±1-order light in the vicinity of the light receiving part of the photodetector 9. Areas B1~B3 and C1~C3. When the detection signals corresponding to the incident light in areas B1, B2, B3, C1, C2, and C3 are B1, B2, B3, C1, C2, and C3 in sequence, the relative inclination angle θe between the optical disc and the optical head optical axis can be passed

θe=(B1+B3+C2)-(B2+C1+C3) detected.

The detection principle of the relative inclination between the optical disc and the optical axis of the optical head will be described below with reference to FIG. 3A and FIG. 3B . FIG. 3A shows the shape of the light spot on the photodetector 9 when the optical disc is perpendicular to the optical axis of the optical head. At this time, the inclination detection signal θe=(B1+B3+C2)-(B2+C1+C3)=0, and it is detected that the relative inclination between the optical disc and the optical head optical axis is 0.

FIG. 3B shows the shape of the light spot on the photodetector 9 when the optical disc and the optical axis of the optical head are in a state of inclination. At this time, the inclination detection signal θe=(B1+B3+C2)-(B2+C1+C3)>0. The larger the relative tilt angle between the optical disk and the optical axis of the optical head, the larger the absolute value of θe. The present invention can detect the inclination angle between the optical disc and the optical head optical axis through the above method.

Moreover, by designing X/Z in the range of 0.08>X/Z>0.008 as mentioned above, the relative inclination angle between the optical disc and the optical head optical axis can be from a small state to a large state, and the angle can be from 0.5° to 5° Within the range, the detection angle range can be set arbitrarily.

In addition, in the present invention, as shown in FIG. 2 , FIG. 3A , and FIG. 3B , by making the direction of the dividing line that divides the light-receiving parts B and C, and the focus position of the 0-order light and ±1-order light that include the vicinity of the light-receiving part The planes are basically parallel, and the wavelength change of the semiconductor laser 1 caused by the temperature change causes the diffraction angle to change, so even if the position of the light spot of ±1 order light shifts, the detection signal will not be affected.

In addition, in this embodiment, the diffraction grating 2 generates sub-beams for detecting the relative inclination angle between the optical disc and the optical head optical axis, but the present invention is not limited thereto, and the plate-shaped optical element 20 shown in FIGS. 4A to 4C can also be used. to get the same effect. 4A is a top view of the plate-shaped optical element 20, FIG. 4B is a cross-sectional view taken along line 4B-4B of FIG. 4A, and FIG. 4B is a bottom view of the plate-shaped optical element 20. Synthetic diffraction patterns 21 and 22 with predetermined curvatures are formed on the front and back of the plate-shaped optical element 20 . The ensemble diffraction pattern 21 and the ensemble diffraction pattern 22 are axisymmetric about an axis 23 parallel to the surface and the back surface. The cross-sectional shapes of the composite diffraction patterns 21 and 22 are saw-toothed or stepped. The above-mentioned distance X can be changed by changing the concavo-convex pitch of the integrated diffraction patterns 21 and 22, and the above-mentioned distance Z can be changed by changing the curvature.

(Embodiment 2)

FIG. 5 shows an example of the overall configuration of an optical disc drive (optical information processing device) 67 according to Embodiment 2 of the present invention using an optical head. The optical disk 7 is clamped by a turntable 62 and a clamper 63 , is fixed on the turntable 62 , and is rotated by a motor (rotation system) 64 . The optical head 60 is mounted on the transfer system 65 , and the light emitted by the objective lens 6 of the optical head 60 moves along the radial direction of the optical disc 7 from the inner periphery to the outer periphery. The control circuit 66 performs focus control and tracking control on the optical head 60 , travel control on the transport system 65 , and rotation control on the motor 64 based on information received from the optical head 60 . Also, the control circuit 66 reproduces the information recorded on the optical disc 7 based on the reproduction signal from the optical head 60 , sends the signal to the optical head 60 and records it on the optical disc 7 .

The optical head 60 is mounted on the inclination detection device shown in the first embodiment. Based on the relative inclination signal between the optical disc 7 and the optical axis of the optical head 60 detected by the inclination detection device, the coma aberration of the main beam can be corrected by known techniques to perform good recording or reproducing operations.

The optical disc drive 67 shown in FIG. 5 can be used as, for example, a storage device (or an external storage device) and built (or plugged in) in a computer, a video recording device, a video playback device, a car navigation system, and the like. In this case, configurations other than the computer, the video recording device, the video playback device, and the storage device of the car navigation system are not particularly limited, and known configurations can be employed.

Any one of the above-described implementations is used to clarify the technical content of the present invention, but the present invention is not limited to such specific embodiments for interpretation, and can be described in the essence of the present invention and the claims. The present invention should be interpreted broadly and implemented with various changes within the scope of the present invention.

Claims (11)

1. An inclination detection device, characterized in that it comprises: a light source; a converging optical system that converges the light beam from the light source on the optical information recording medium; the light beam from the light source is separated into a main light beam and at least 2 an optical separation device for the sub-beam; and a detection device for detecting reflected light from the optical information recording medium, The focus position of the first convergent light of the main beam directed toward the optical information recording medium and the focus position of the second convergent light of the sub-beam toward the optical information recording medium are on the optical axis of the converging optical system direction and the direction perpendicular to the optical axis direction are different from each other, The optical information recording medium is detected by using the detecting device to detect the size of the light spot formed on the detecting device by the reflected light of the sub-beam reflected on the optical information recording medium. and the relative inclination between the optical axis of the converging optical system. 2. The inclination detection device according to claim 1, wherein the light of the condensing optical system between the focal position of the 1st condensed light and the focal position of the 2nd condensed light When Z is the distance in the axial direction and X is the distance in the direction perpendicular to the optical axis of the converging optical system, X and Z satisfy 0.08>Z/X>0.008. 3. The inclination detection device according to claim 1, wherein the light receiving part of the detection device, which receives the reflected light reflected by the sub-beam on the optical information recording medium, is divided by a dividing line into three regions, and the dividing line is substantially parallel to the plane including the focus positions of the reflected lights reflected by the main beam and the sub-beam on the optical information recording medium. 4. The inclination detection device according to claim 1, wherein the optical separation device is a simple diffraction grating. 5. The inclination detection device according to claim 1, wherein the optical separation device is a plate optical element, and the plate optical element is provided with the first comprehensive diffraction pattern with curvature on the first face; A second comprehensive diffraction pattern is provided on the second surface opposite to the first surface, and the second comprehensive diffraction pattern is symmetrical to the first comprehensive diffraction pattern with respect to an axis parallel to the first surface; The cross-sectional shapes of the first and the second comprehensive diffraction patterns are saw-toothed or stepped. 6. An optical head, characterized in that it has the inclination detection device according to claim 1. 7. An optical information processing device, characterized in that it has: the optical head according to claim 6; a drive mechanism for moving the optical information recording medium relative to the optical head; The signal obtained by the optical head controls the optical head and the driving mechanism. 8. A computer comprising the optical information processing device according to claim 7. 9. A video recording device comprising the optical information processing device according to claim 7. 10. A video playback device comprising the optical information processing device according to claim 7. 11. A car navigation system comprising the optical information processing device according to claim 7.

Images